Blood Typing

Blood typing is a technique use to inform what specific type of blood you have. Your blood type is subject to the presence of certain proteins, called antigens, on your red blood cells.
Blood is grouped according to the ABO blood typing system. Your blood group (or bloo type) is the result of the types that have been passed down to you from your parents.This method breaks blood types down into four categories:

Type A

Type B

Type AB

Type O

How the Test is Performed

The puncture site,–usually the inside of the elbow or the back of the hand– is cleaned with a germ-killing product. An elastic band is placed around the upper arm to apply pressure, which causes the vein to swell with blood. Then blood is drawn from a vein with the insertion of a needle into the vein, and the blood is collected into a tube. During the procedure, the elastic band is removed to restore circulation. Once the blood has been collected, the needle is removed, and a band-aid or gauze is applied.

In infants or young children, the area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. If there is any bleeding, a bandage may be applied to your children.

There are two laboratory steps can accurately determine your blood type. First, your blood sample is mixed with antibodies against type A and B blood, and the sample is examined to see if the blood cells agglutinate.

If blood cells stick together, it means the blood reacted with one of the antibodies.

The second step is known as back typing. There is a liquid part of your blood without cells called serum, which is mixed with blood that is identified to be type A and type B. Persons with type A blood have anti-B antibodies, and those with type B blood have anti-A antibodies. Type O blood contains both types of antibodies.

Blood typing is also performed to tell whether or not you have a substance called Rh factor on the surface of your red blood cells. Rh typing uses a method similar to ABO typing. If you have this substance, you are considered Rh+ (positive). Those without it are considered Rh- (negative).